A new study published in Microsystems & Nanoengineering (DOI: 10.1038/s41378-025-01019-w) demonstrates a tiny ultrasound array implanted under the skin that can continuously monitor blood pressure with high accuracy. The device, developed by researchers from the University of California, Berkeley, and collaborators, addresses longstanding limitations of conventional blood pressure monitoring methods, such as discomfort, motion artifacts, and poor alignment.
Hypertension is a leading cause of heart disease and stroke worldwide, and continuous blood pressure tracking is critical for prevention. However, traditional cuff-based measurements are intermittent and disruptive, while wearable sensors like photoplethysmography (PPG) or ultrasound patches suffer from shallow penetration, gel dependence, and sensitivity to misalignment. Implantable sensors have been explored but often require invasive arterial placement or provoke foreign-body reactions.
The new system is based on a 5 × 5 mm² piezoelectric micromachined ultrasonic transducers (PMUTs) array, comprising 37 × 45 elements. Each PMUT has a 29-µm diaphragm operating at about 6.5 MHz, providing high axial resolution and strong echo penetration. The dual-electrode bimorph design enhances acoustic output, and the array is fabricated using CMOS-compatible processes for uniformity.
To measure blood pressure, the device emits ultrasound pulses and captures echoes from the anterior and posterior walls of a nearby artery. The time-of-flight between these echoes is converted into a real-time diameter waveform, which correlates with blood pressure through vessel stiffness models. Bench-top experiments confirmed a linear relationship between diameter and pressure. Notably, simulations showed that wearable systems can lose up to 60% signal strength with just 1 mm of misalignment—an issue the implanted design avoids by maintaining stable coupling.
In vivo testing in an adult sheep, the PMUT array was implanted above the femoral artery. The device captured detailed pressure waveforms, including the dicrotic notch, and matched gold-standard arterial line measurements within −1.2 ± 2.1 mmHg (systolic) and −2.9 ± 1.4 mmHg (diastolic). These results indicate clinically reliable performance without the drawbacks of cuffs or wearables.
“The study shows that ultrasound-based implants can achieve the stability and precision required for continuous blood pressure monitoring,” said the corresponding author. “By capturing arterial diameter changes directly through subcutaneous sensing, the device avoids issues like gel dependence, environmental noise, and misalignment.”
This implantable system represents a promising alternative for patients needing continuous, unobtrusive measurement. Its stability against tissue growth, motion, and interference makes it suitable for long-term hypertension management, early detection of cardiovascular abnormalities, and integration into digital health platforms. Future advances, such as beamforming to mitigate positional shifts and data-driven analytics for individualized risk prediction, could further expand clinical utility. Ultimately, this technology may enable preventive care by providing continuous, high-fidelity cardiovascular data in real-world environments.
The research was supported by BSAC (Berkeley Sensor and Actuator Center). The study is published in Microsystems & Nanoengineering, a journal by Chuanlink Innovations (http://chuanlink-innovations.com).
